DYEING AND CALICO PRINTING.

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We append a sample of cloth dyed with this colour by the firm of Messrs.Walter Crum and Co.

To fix this colour, the goods, after printing, are steamed for half to onehour.

The raw materials for the manufadture of artificial ultramarine are —(i). Silicate of alumina, as free as possible from iron, the kaolin of Cornwallbeing preferred. (2). Calcined sulphate of soda. (3). Calcined soda.(4). Sulphuret of sodium, a by-produdt of the manufadture. (3). Sulphur.(6). Pulverised coal or charcoal. The clay is washed with water, dried,ignited, and ground to a very fine powder. The sulphate of soda must be freefrom lead or iron. Potassium salts will not form ultramarine ; barium saltshave the property (see “ Chemical News,” vol. xxiii., pp. ng, 142, 204).Alkali works supply the calcined soda, which should contain at least .85 per

Ultramarine.

cent of carbonate of soda. Caustic soda may be substituted. The sulphurand the carbon are both very finely pulverised.

There are three methods of preparing ultramarine generally followed : theyresult in—

a. Sulphate-ultramarine;

/ 3 . Soda-ultramarine;

y. Silica-ultramarine.

a. The preparation of sulphate ultramarine is included in two stages :—

1. Preparation of green ultramarine.

2. Conversion into blue ultramarine.

(1). The kaolin, sulphate of soda, and charcoal are all finely pulverised ; orif solutions of sulphate of soda, soda, and sulphide of sodium are used insteadof powders, the kaolin is stirred with the solution, and the mixture evaporatedto dryness and ignited. The materials are employed in such quantity thatthe soda shall saturate half the silica of the kaolin, and shall be present in